Perfetto sources are in src/.

protos/ contain manually tree-shaken protobuf message definitions used by the VM as well as *.pbzero.h files generated from these definitions.

Note: experiments show that three-shaking protobuf messages does not have an impact on code size of the VM because protozero generates header only code for serializing protobuf messages which tree-shakes very well.

This is not the case for Dart code we ship in pkg/vm_service_protos: using pristine message definitions (as given in Perfetto sources) would require including large amount of generated Dart code into this package, which will never be used by consumers like DevTools. This code does not tree-shake by default because each message is strongly connected to all of its submessages (though our compiler toolchains provide protobuf aware tree-shaker to reduce the size of the code).

Thus for now we choose to use manually tree-shaken protos.

Updating Perfetto

After updating Perfetto regenerated *.pbzero.h files by running:

$ dart third_party/perfetto/compile_perfetto_protos.dart